text:
What would be the best fan duct design to achieve maximum thrust?
I have a few brushless motors and I am trying to get the best thrust out of each motor. I am busy doing some research but can't get a clear answer. What would be the best fan duct design to achieve maximum thrust?
Project: mini hover bike prototype with 2 or 3 motors. Duct size doesn't matter at this point.

obviously the most efficient choice is no duct but use a prop, especially you when you don't care about size

@user3528438 Not necessarily. Shrouded propellers do deliver higher thrust than unshrouded ones, especially if the clearance between propeller and duct is very low.

It all depends on the specific setup for the motor and props. With the correct setup you can increase thrust and reduce power consumption by to 50-60%. (so I have read). I'm going to use @Koyovis research and 3D print some test ducts and props.

You could take a look at the ducting on the Moller flying car also  https://moller.com/  The M200 had 8 ducted fan motors.  https://www.moller.com/brochures/Neuera-Brochure.pdf

"The M200G Neuera Volantor
A revolutionary 2-passenger VTOL ground effect vehicle"  Wonder if electric motors could substitute for fuel powered motors now? Battery technology has come a long way.

It's not easy to find research on small ducted fans. I did come across this interesting masters thesis from 2009, which does show some relevant results - at low propeller speeds.
Duct design
The document describes three duct designs, one with a variable bypass inlet and two simpler ones. The simplest one is made from PVC tuning and a foam inlet lip:

Geometric information is given as:

Inner diameter = 14.5"
Duct Chord = 4"
Duct Length (C/D) = 0.28

Maximum Thrust
One of the results of the project is that a ducted propeller delivers more thrust than an un-ducted one. Here is one of the results, listing $C_T$ as a function of tip Mach numbers - which are really low and therefore hard to generalise into practical rotor and fan configurations.

Tip Clearance
Best results were obtained with a propeller with square tips with the smallest gap between propeller and duct that could be achieved. This was a 3-blade propeller, but the research project was severely limited by the small motor used, and therefore low maximum torque that could be exerted on the propellers.

Thanks, great answer! The information and linked document will definitely push me in the right direction. I guess there is no 1 answer as every motor, prop, number of blades, motor torque etc. differs.


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How can I renew my non-current Indian CPL?
I have not renewed my Indian CPL since 2001 and would like to renew it. what is the procedure as the CAR says nothing about renewing licence below 5700 kgs category.
Since there is no rule what can be done. I am flying regularly on my FAA licence.

This is for CAA , each country might have a different rule but in general this is the rule . If you haven't flown in India since 2001 then your license has been expired. So I assume that if you have any other license valid , you have to go to Indian civil aviation with your current  log book and they will request a confirmation from the country that you have got your license from to be sure that your license is still valid in that country.Then you have to do the conversion requirements which generally are 4 exams (for most countries are Law,HP,Nav, Met) and then you also have to go to any ATO in India and you must undergo sufficient ground and flight training for the same category aircraft that you have your other license on , and then do a oral exam and flight test .
If you haven't flown in the last 10 years , you have to do all CPL exams again .
Good luck.

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text:
Does the reference for AGL include obstacles?
Let's say a plane flies 10m above some trees, that themselves are 10m above the underlying ground. Would that be 10m or 20m AGL?
Or, in more abstract terms: What exactly is the reference point for AGL? The actual ground that you would stand on as a pedestrian? The point where you would first impact something (even if it's just a very lightweight sprig)? something else?
How does it work with objects like high bridges, that you could fly below but could still impact on a higher altitude?

two things, List what country this is for, for more accurate answers. However, flying under bridges should be generally avoided. This should not be confused with other non-aeronautical places that AGL is used and in that case it refers to the actual ground. The case in the US refers to how tall an antenna needs to be before it is lit and painted as an Air Navigation Hazard -- 199 feet (60m) or less and it wont be lit.

AGL is "Above Ground Level".  Ground is the reference.  Trees, buildings, towers, and such are obstacles.  Pilots need to be aware that obstacles exist.  Most of the smaller ones can be addressed by just flying at a safe altitude.  This is covered (in the US) by the following Part 91 rule:

§91.119   Minimum safe altitudes: General.
  Except when necessary for takeoff or landing, no person may operate an
  aircraft below the following altitudes:
(a) Anywhere. An altitude allowing, if a power unit fails, an
  emergency landing without undue hazard to persons or property on the
  surface.
(b) Over congested areas. Over any congested area of a city, town, or
  settlement, or over any open air assembly of persons, an altitude of
  1,000 feet above the highest obstacle within a horizontal radius of
  2,000 feet of the aircraft.
(c) Over other than congested areas. An altitude of 500 feet above the
  surface, except over open water or sparsely populated areas. In those
  cases, the aircraft may not be operated closer than 500 feet to any
  person, vessel, vehicle, or structure.
(d) Helicopters, powered parachutes, and weight-shift-control
  aircraft. If the operation is conducted without hazard to persons or
  property on the surface—
(1) A helicopter may be operated at less than the minimums prescribed
  in paragraph (b) or (c) of this section, provided each person
  operating the helicopter complies with any routes or altitudes
  specifically prescribed for helicopters by the FAA; and
(2) A powered parachute or weight-shift-control aircraft may be
  operated at less than the minimums prescribed in paragraph (c) of this
  section.

Following (a) and (b) is the safest course. Para (c) provides a great deal of latitude to fly low but has significant risks.  Agricultural pilots fly very low all the time.  But ask any one of them and they'll be glad to discuss all the stuff they've hit.
These rules are primarily directed at VFR flight. Under IFR, ATC clearances are designed to ensure operating at safe altitudes, clear of both terrain and obstacles.
For larger obstacles such as towers and bridges, they are charted.  As you can see on the clip below:

There are a number of towers in a relatively small area.  In this case there is the underscored BITHLO TOWERS label to bring attention to them. Adjacent to the tower icons are two numbers. The number not in parentheses is the height in MSL.  In parentheses is the height AGL.

Also, don't crop dusters generally fly in clear, calm weather?

@Sean Winds do cause problems when spraying, so relatively calm weather is typical.  They fly VFR, but I wouldn't say it's always "clear" since they mostly operate in Class G airspace below 1200 ft AGL where minimums are 1 mi visibility and remain clear of clouds.  Flying with barely 1 mi visibility with a low ceiling doesn't give you many options even over a very large farm.

The AGL is mostly taking reference to the Radio Altimeter. The RA is measuring the distance between the ground and the aircraft through waves sent to the ground and receive the rebound of it. The time between the ping and the pong gives you the distance between the aircraft and the ground (like a sonar).
See: https://en.m.wikipedia.org/wiki/Radar_altimeter
That being said,the reference of AGL is random. Because the RA should catch the top of the tree and if you were flying at a constant ASL with trees or hills below you, you will see your RA change all along your leg.

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Optimising Continuous Descent Approaches (CDA): Seeking Strategies and Rules of Thumb
Ideally, approaches should be executed as a continuous descent approach (CDA), maintaining idle thrust and only levelling off (or reducing vertical speed to <500 fpm) briefly to reduce speed, while still keeping the thrust at idle.
While I cannot speak for every region, in Europe, executing a CDA is widely regarded as the most beneficial method of flying. It conserves fuel, as engines are at idle, and significantly reduces noise pollution. The majority of European airports support CDAs, although there are exceptions. For instance, Bergerac Airport in France necessitates maintaining an altitude of 2,500 feet for an approach to runway 27.

As a Boeing 737 pilot, I am keen to learn about any rules of thumb or strategies that other pilots employ to effectively execute a Continuous Descent Approach (CDA), particularly when piloting a Boeing 737. I aim to stay in VNAV, but I am also prepared to utilise LVL CHG and V/S as required. Our company's Standard Operating Procedures recommend using a 10nm ring for the landing runway, and I make use of the altitude range arc (known as the “green banana”) to enhance situational awareness.
Let’s take London Gatwick as an example:

ICAO Chart ILS/DME RWY 26L from UK AIP
In my flight planning I may work out what maximum altitude I need to be at 10nm out using this calculation:
Altitude at 10nm = Altitude at 5nm + 5 x (altitude loss per nm on glideslope)
= 1840 + 5(1840-1520)
= 3440 ft

The chart gives the 5.5nm to intersect the glideslope at 2000', but I may also write down what altitude I would intersect the glideslope at 3000':
At 3000’, mileage required = (3000 - Aerodrome Elevation)/(altitude loss per nm on glideslope)
= (3000-203)/(1840-1520)
= 8.7nm

I would write these 3 altitude-distances down and refer back to them during the descent to make sure I am on profile. I would cross reference my progress with the "green banana" and 10nm range ring, and of course the VNAV profile (737 specific).

What effective rules of thumb or strategies can be employed to effectively execute a CDA?

When considering altitude at specific distances, such as 10nm out, do you rely on pre-calculated altitude-distances, or do you employ a more efficient, quicker mantra?
Are there any more reliable or simpler techniques to enhance situational awareness during a CDA, ensuring adherence to the desired glide path without deviating too high or low?
In scenarios such as encountering a stronger than anticipated tailwind, how do you adjust or preemptively manage being high on the approach? What indicators are you looking for to inform you that you are high on approach.

Personally, I find that the most critical point is from ~7000' to ~4000', trying to balance the best moment to decelerate and/or keep on the profile.

When I was on a team that developed (what we called) Continuous Descent Arrivals in the US the team was also comprised of representative pilots from the major air carriers servicing that airport. As I recall, the FMS flew the arrival/approach automatically. Does your aircraft not do this?

@RetiredATC I’m not sure what it is like in States, but in Europe we rarely follow the actual STAR arrival. By radar vectoring, we will often expect (quite dramatic) shortcuts on the STAR or a vector to a 10nm final etc. So we find that we can’t accurately predict and therefore can’t program the true arrival in then FMS. Even if you fly on the arrival track exactly, a tailwind may get you high on profile (quite insidiously). So we can rely on the FMS to a certain extent, but situational awareness of vertical position is also incredibly important.

I've seen the technique of putting the green xx mile arc around either the runway or the FAF waypoint, and I'm not a fan. There are too many variables at work to make any particular answer of being at some altitude or some airspeed when reaching that arc generally reliable.  Simplest counter-example: being 30 miles from the airport at 10,000' and 250 knots is good gouge when you're on base; if straight-in, you have too much energy; if on downwind, you're below an ideal profile.  Same sorts of limitations exist with an arc around the FAF.
What I've found works better is primarily considering altitude when on an RNAV approach or an arrival that will transition into an instrument approach with no or minimal level segments ahead.
Take as a starting point that being at 2,000' above the runway on a 3-degree path (so about 6 NM track distance to go), with flaps at 5, and speed below the clean maneuvering speed (not necessarily all the way slowed to the Flaps 5 min maneuvering speed, but somewhere between the -UP and the -5 markers)... for most reasonably normal days, if I'm at that state passing 2,000' I can lower the landing gear and configure normally and be easily stabilized by 1,000' above the runway.  Strong tailwinds will mean backing that out a bit, but in general, on path at 2,000' with flaps 5 is a good place to be, dropping the gear at about that point.
So if you're on a procedure that keeps you roughly on a 3 degree path, what do you need to be doing above 2,000' to achieve that state there?  Evaluate your winds and gross weight and existing airspeed and decide when to start extending flaps to get there.  If you're 20 knots above the -UP marker with light winds, then maybe 3,000' or slightly below will be a comfortable point to make the initial flap extension.  If you're assigned a speed right above the -UP marker, then you can probably delay extending the flaps until maybe a mile outside the 2,000' point and that can work comfortably. If you're already at Flaps 1 or 2 and stable at the maneuvering speed for that configuration, then you can hold that all the way to 2,000'.
On the other hand, if you're at 250 knots and on a 3 degree path, you probably need to be starting at 4,000' getting rid of energy -- and if you're much lower than that and still fast, then leading with the landing gear may be necessary. A clean 737 on glide path doesn't bleed energy very quickly, and with a tailwind, it may not slow at all without significant  help... option 1 would be extending the speed brakes to get the speed down to 240 (i.e. 10 knots below the placard limit for initial flaps) then flaps 5; option 2 is extending the gear immediately, and option 3 is everything: gear+speedbrake+Flaps 5 until you can extend more flaps  -- which is a "save" maneuver and not a recommended way to plan to slow and configure! (If you're having to do that, the best choice -- if your procedures allow it -- is to configure all the way to landing flaps in level flight before resuming the descent... this gets the most drag out soonest so it's working for you the longest.)
All of this is clearly a discussion of technique and requires some sense of what "looks about right" so as to achieve the landing configuration in a timely (i.e. stabilized) but not drastically early manner; until that sense of what looks right becomes somewhat developed, err on the side of configuring early... the extra gas burned in dragging the gear an extra minute or two is far less than the gas burned in a go-around & extra trip around the pattern. But, as that sense does start to develop, I find that watching altitude and comparing my state in that regard to the altitudes on a straight-in approach tends to be the best guide -- better than using distance-from-the-FAF in isolation, for instance.

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text:
METAR, TAF, NOTAM, PIREP - which authority for contractions?
Aviation obviously is known for is a.c.r.o.n.y.m.s. and abbreviations.
My question is: who controls the abbreviations/contractions for the below services? If you are aware of a source document showing the contractions I would very much appreciate a link or document name. (edit: USA sources / services).
I have made suggestions in parenthesis for METAR and NOTAMs, but I am not sure if they are the definitive source.

METAR (NOAA / FMH-1?)
TAF (I have no idea, same as METAR?)
NOTAM (combination FAA & ICAO? This doesn't really look like a source document.)
PIREP (no clue)

If I am forgetting any similar services which also use acronyms I would appreciate a heads-up so I can add to the question!
Thanks for your time.

What is the purpose of this list? Once you know that the METAR format is controlled by the World Meteorological Organisation with exceptions for North America (WMO and FMH-1), what are you going to do with this?. Other countries may have their own exceptions, and countries not signed up to the WMO may do their own thing. Do you want to cover all those as well?

Purpose of list: I want to know where to look for primary sources. What I will do with list: read the primary sources. I am only asking about USA sorry for ambiguity.

@CatchAsCatchCan "Why do you want to know?" is a strange thing to ask on a website devoted to answering peoples' weird questions.

Who controls?
Meteorology and aviation are fields impacting all countries, and where phenomena and aircraft cross State boundaries. Activities in these domains require an international collaboration and harmonized practices. The United Nations organization is made for that. Each UN State member has representatives in UN agencies to provide inputs and agencies issue recommendations and standards that can be implemented in the State members local regulations.
In the US, FAA is the US agency for aviation matters and NOAA the agency for weather matters. They work with their counterparts in the corresponding UN agencies: ICAO and WMO.
This collaboration is similar to the collaboration between ICAO and ITU, another UN agency, in the domain of radio spectrum use, radio transmission standards and navaids.
Aeronautical reports and forecasts
Aeronautical reports and forecasts are defined jointly by two agencies of the United Nations:

ICAO in the Chicago Convention (Annex 3, Meteorological Service for International Air Navigation) and

World Meteorological Organization in WMO Meteorological Service for International Air Navigation.

The two key documents for weather codes are:

ICAO Doc 8896, Manual of Aeronautical Meteorological Practice

WMO Aerodrome Reports and Forecasts

The last one is likely the one you need to decode some cryptic weather message quickly.
Other WMO relevant documents, also available online, relate codes and practices to the general meteorological field, e.g. different manuals on codes, like WMO Manual on Codes, Alphanumeric Codes (human readable form, sort of) and Manual on Codes, Binary Codes (data storage and exchange).
ICAO ensures meteorological services standardized by WMO are adequate for aviation. Related formats include forecasts:

$\small \sf WAFS/SIGWX$: Global forecasts of significant weather,
$\small \sf TAF$: Aerodrome forecast,
$\small \sf GAMET$: General aviation forecast,

and reports:

$\small \sf METAR$: Aerodrome routine meteorological report,
$\small \sf SPECI$: Aerodrome special meteorological report,
$\small \sf VOLMET$: Meteorological information for aircraft in flight,
$\small \sf SIGMET$, $\small \sf AIRMET$: Specified en-route weather phenomena.

Aircraft-based observations: PIREP, AIREP, AMDAR
Originaly a PIREP (pilot report) is an informal radio report from a pilot to ATC. Methods and codes are mostly defined by the national aviation agency, FAA for the US. See the FAA PIREP form. Some information is provided in WMO Guide to Aircraft-based Observations.
However with the advent of automated sensors in aircraft, formatted and automated reports are defined as AIREP (special air report) and AMDAR (aircraft meteorological data relay) messages, transmitted using ACARS or ASDAR. Both reports are described in ICAO Doc 8896, Manual of Aeronautical Meteorological Practice and WMO Guide to Aircraft-based Observations, both already mentioned.
NOTAM
NOTAM (notice to air missions) is a different kind of information. an important part of the aeronautical documentation, describing information which cannot be permanent, and thus cannot be included in the regular State aeronautical information publication (e.g. US AIP). They are standardized by ICAO in Annex 15, Aeronautical Information Services
Technical details are found in Doc 10066, Aeronautical Information Management (PANS-AIM) and Doc 8126, Aeronautical Information Services Manual.

I know comments arent supposed to be used for "thanks" but there are a lot of good resources you put in here. So... thanks!

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text:
What kind of plane could be leased back to a flight school?
I was having a brief chat with the CFI at a local club/school and he talked about lease back, assuming that the maintenance and insurance is paidfor by the lease back and isnt an issue the question is this, what sort of aircraft can I buy to lease back, is there restrictions on the age or hours on a hire aircraft or can any 2 seater do the job, I am getting back into flying after a long break and want to get back into aerobatics, so something like a 150/152 aerobat would be ideal, there are no aerobatic planes in my local area so there is an incentive on both sides to do this ?

If it is in the US, it must be of US registry. The only requirement is it must be a certificated aircraft, no experimental or home builts. The only other requirement is it must have an annual and 100hr inspections until the next annual. So long as the airplane meets the maintenance inspections, their are no other restrictions.

If it sounds to good to be true...

The owner or manager of the school can probably tell you what type(s) of aircraft they’d be interested in leasing back from you. Maybe keeping the fleet common is a goal, or adding a taildragger is under consideration, or adding something with particular avionics, or preferring particular avionics, or ...

You need to talk to somebody who is doing a leaseback with the flight school to see what they are experiencing. Leaseback contracts can vary quite a bit. You also need to talk to your insurance company because your insurance rates may go up quite a bit. Leasebacks can help defer some costs, but they have drawbacks (you have to work around the aircraft's schedule, students banging up the airplane, etc).

See: AOPA Aircraft Owners Guide to Aircraft Leasing (Leasebacks)

I'm not entirely sure what you're asking here. You could leaseback any aircraft, if the contract is acceptable to both the school and the owner. I may be wrong, but it sounds like you're asking if leasebacks are a good idea or not, and that's a highly subjective question that we can't easily answer here: a lot depends on your personal situation, the contract terms, the insurance implications etc.

It's for the UK, was just thinking out loud, but there's a massive difference between, for example a Robin 2112 @ £20k and a Pitts S2 at £50k, just browsing ads and seeing what interests me at the moment, trying to make it all work out :)

The ONLY reason to do a leaseback is if you've run all the numbers and are planning to do it as a business, and you can afford to take a loss. Do NOT do it if you think you will reduce the cost of flying -- in the vast majority of cases leasebacks are a subsidy to the club. If you want to get into aerobatics -- great! Rent an aerobatic airplane!

BTW in the US a leaseback is not an operation "for hire or compensation" unless the club provides everything -- airplane, instructor, fuel, etc. In the usual scenario where CFIs are independent contractors, it's not a "for hire" operation and no 100-hour is required; and the airplane does not have to be certificated.


text:
Why would a pilot leave the gear down after takeoff for extended period of time?
Normally when an aircraft departs, the landing gear is retracted shortly after the aircraft is airborne. While watching aircraft departing from an airport in my city, I noticed, that occasionally the pilots leave landing gear down for many miles (10NM or possibly more). What is the reason for this, are they trying to cool down something?

Is it the same type or aircraft each time you see this, if you're able to tell? Also, have you ever observed them first retracting the gear and then, after gaining some altitude, lowering it again for awhile?

I saw this happen twice, in both cases they were A333 from two different airliners. The gear was left open since the a/c got airborne, and both aircraft continued with the departure as per normal SID.

Correction to my previous comment: it was A333, and then B788.

Location information could provide a hint. Is it a hot place ?

Kebs: location Sydney, Australia, during winter (around 17*C during the day)

It's usually for one of two reasons:
Brake temps are displayed in the cockpit and if the temps were elevated from a lot of, or excessive, brake use during taxiing, the capt may delay retraction until the indications come down, mainly to avoid gear bay overheat indications. This will be more common on airplanes that have more idle thrust than necessary to roll at normal taxi speed, which can cause a tendency to ride the brakes.  CRJ200s, which can get going pretty fast on idle thrust with both engines running, are really bad for this.
Also in winter on a departure from a slushy runway, retraction may be delayed to try to blow off as much slush as possible since once the slush freezes, it can immobilize the wheels, preventing normal spinup on the next landing (if it's still cold at destination).

Some Airbus aircraft (e.g. A320, A330) do not have wheel well fire/overheat detection. Instead, the BRAKES HOT ECAM procedure requires that they re-extend the gear until the brakes cool below the ignition temperature of leaking hydraulic fluid. (This answers the OP's comment that they saw it on A333s)

Cooling the gear after takeoff is one likely scenario, if the aircraft had only a short time on ground between landing and takeoff. Another scenario (from memory  - standing by to be corrected) is an inoperative wheel brake on one of the main gear wheels, where sufficient time must be allowed after takeoff to ensure the wheel is spun down before retraction.


text:
What is the aerodynamic advantage to a cuffed wing like the Cirrus SR-22?
What is the aerodynamic advantage to a cuffed wing like this Cirrus?

I'm sure I read about how wings are designed to account for stalling at different times in this e-book, but skimming thru quickly I don't see it. http://www.av8n.com/how/#contents

related: https://aviation.stackexchange.com/q/30921/1467

Related: What does the zig-zag pattern on Hawker Hunter's leading edge represent?

Here we go:
http://whycirrus.com/engineering/stall-spin.aspx

Spin Prevention
  Cirrus chose, in the very earliest stages of designing
  the SR20 to take on the challenge: to minimize the risks associated
  with inadvertently stalling an airplane. The approach chosen was to
  employ wing technology developed by NASA reducing the potential for
  spin entry after an inadvertent stall. The most visible aspect is the
  discontinuous leading edge dividing the wing into distinct parts.
  ...
  How does this wing design work?
  The outboard section of the Cirrus wing flies with a lower angle of
  attack than the inboard section. When the inboard section, which
  produces much of the lift, stalls the outboard section, where the
  ailerons are, is still flying. The result is that a stalled Cirrus
  airplane can be controlled intuitively using aileron.

That makes a lot of sense, nice find! It kind of makes me wonder why we don't see it on more designs though

Reading the page, it seems to appear on other more current designs as well.  I have micro-vortex generators on my plane that keep the airflow laminar in place longer with higher angle of attacks, keeps the airplane really responsive at low airspeeds and harder to stall.  https://microaero.com/  They work really well, help to really shorten & soften my landings.

Good luck to anyone that gets used to those handling characteristics when they next fly something that doesn't have this feature or lots of washout!

It's not hard to adapt.  I had to fly an old Cessna 172 for a BFR so I could move my vortex generator equipped Cessna 177 on a ferry flight for a long overdue annual inspection. I hadn't flown in 13  years.  The 172 was kind of doggy handling wise, compareed to the 177, and I had never flown one, but it was easy enough to stall it and recover, and the speed down final was similar.  I just couldn't let it get quite as slow as I would in the Cardinal.

@CrossRoads: Are you aware you keep posting broken links? It looks like you keep putting them in <> for some reason, and the > gets interpreted as part of the link.

@Geoff: It is a kludge that is slapped on a misbehaving wing after design. A better way is to design washout into the wing and to use different airfoils for the inner and outer wing. This step causes a jump in lift which is bad for induced drag. In short, the wing becomes less efficient in creating lift that way.

I thought <>  was what was used for links. What's the correct method?


text:
What is the maximum altitude ATC would deal with?
What's the maximum altitude ATC would deal with?
Any example of jets service ceiling certified for above 45.000? Commercial & Business jets?

The max altitude ATC would deal with is the transition altitude. Above that it's flight levels.

There are many examples of aircraft with high service ceilings. While most commercial aircraft have service ceilings of FL410 and rarely fly even that high, many business jets have a service ceiling of FL510, such as the Dassault Falcon 7X, Gulfstream G650, and Bombardier Global Express.
That being said, military jets can fly higher and will be talking to ATC while in their airspace. Fighter jets are capable of high altitude flight, and planes like the U-2 and Global Hawk still fly up there as well.
In the US, all aircraft from FL180 to FL600 must be in contact with ATC, but above this they are not required to. ATC will still provide services when able though.

Your link to the U-2 wiki was apparently lost when they ascended past FL600...

@TemporalWolf haha, thanks for letting me know!

If above FL600 they are not required to be in contact with ATC, other than TCAS, what prevents collisions?

@user1997744 I am no expert and have no clue how cockpit looks like (demonstrating my knowledge about planes); but I think planes that fly that high have on board radar - preventing collisions.

@user1997744 the fact that there are so few airplanes that ever fly that high, and they will probably prefer to stay in contact with ATC for safety.

@user1997744 Above FL600 is Class E airspace, which is "controlled airspace" and if aircraft are going to be flying in conditions such that they cannot see out the windshield then they need to be in communication with ATC. If the conditions do allow them to see out the windshield then they use their eyes to avoid collisions (that and the fact that almost nobody is up that high). This Class E airspace also exists at much lower altitudes, and again if the weather conditions are good pilots "see and avoid" if they are not in contact with ATC.

There is no maximum altitude for ATC service. ATC will deal with anything that flies over their airspace.
In the US, Class A airspace ends at FL600. Meaning if you fly above 60,000 feet (pressure altitude), you are not required to contact ATC, because it is Class E airspace. But that does not mean ATC will deny talking to aircraft at that altitude.
Practically speaking, very few aircraft (if any) can get above FL600. Chances are if you can get there, you are in an experimental military aircraft or spaceship.
Flights above FL400 are common for private and business jets. They are managed by ATC.

The other answer are correct that above FL600 you no longer need to be in contact however its worth noting there is some interesting historical implications to this.
The only civilian aircraft that routinely operated above the majority of other aircraft was the Concorde, which during its time cruised up around FL500. In his interview on Omega Tau one of Concorde pilots discusses this very situation. Essentially above ~FL450 they were allowed to transition altitudes as they saw fit and without contacting ATC essentially since they knew no one else was up there. He mainly discusses it in the context of fuel burn and how as the aircraft burned fuel it had a tendency to slowly drift up. ATC allowed them to do this (and not stick to an assigned altitude) as they could not really drift up into anyone.

wow thanks that helps me honestly :) didn't know they could change altitude without contacting ATC.

They could be in contact with ATC, but simply given a block altitude clearance, FL 500 block 600 or something. While their autopilot certainly could maintain a precise altitude, it's more efficient to perform the slow climb as fuel burns off, so that's what the block altitude clearance allowed them to do. You sometimes hear aircraft getting block altitude clearances, although it's not common.

Block altitudes are often requested when the air is turbulent and maintaining altitude becomes difficult, especially for small aircraft crossing a weather front where the winds are changing a lot as one example.

@RalphJ in the podcast he does not really touch on that but makes it seem as though that was not the case and they were aloud to drift around merely because no one was up there.


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What are the standard ATC light signals and emergency messages?
Apart from 'mayday' which other common emergency messages are used? Is there any regulation regarding them?
Any other light are used by ATC than these? : https://learntofly.ca/wp-content/uploads/2010/11/ATC-Light-Gun-Signals.gif
Is it the same Emergency messages and  Light signals used worldwide or are they different US-Europe ?

Related, although you seem to be asking two different questions and it might be better to ask them separately.

In the US,controllers may also treat things as if there were an emergency even tho you may not have declared one.  If they start asking about souls on board, you're getting the emergency treatment.

Questions should include all information required to answer them, rather than requiring people to follow links to get the information.

If you are asking about radio telephony then,

b. A pilot who encounters a Distress condition should declare an
  emergency by beginning the initial communication with the word
  “Mayday,” preferably repeated three times. For an Urgency condition,
  the word “Pan-Pan” should be used in the same manner.

There is Pan Pan which is covered here, although that is typically used for an "urgent" situation.
Primarily there is Mayday for emergencies.
There is simply "I have an emergency...." (or if it’s potentially less urgent “a problem” r.e. Apollo 13) however this is not the preferred method.

Those are the three big ones and will get the attention of a controller as well as alerting other pilots on the frequency that there is a problem in the area.

As for the other part of your question, the light signal chart you linked is for tower to aircraft communications when radio is not available. These signals are only used when the aircraft is in close (visual) proximity to the tower.

I don't think anyone aboard Apollo 13 stated that they had "an emergency", and there certainly was no need for Mission Control to tell them that. I know that the crew's first report after the oxygen tank explosion was "we've had a problem". (Not "we have a problem".) However, I'd be happy to be set straight if you can provide a reference.

Those signals are regulated by ICAO Annex 2 rule of the air:
https://www.icao.int/Meetings/anconf12/Document%20Archive/an02_cons%5B1%5D.pdf
Therefore international.Some other ground signals are indicated there but as far as light signals the ones you showed are the only ones.

That is not specific at all.

Dear Sanmer, i am sorry if i wasn’t more precise. Let me be more specific then.... MAYDAY and PAN PAN are the only ones used. Again the document I submitted is the reference internationally. Different authorities might have slight differences from this standards. Have a look from page 34 onwards i believe.   To summarise and be specific:  1/Other than mayday and pan pan the answer is no.                 2/Regulation is down to every local authority but the top authority is the ICAO

@Heliomaster Please [Edit] your answer to clarify in response to comments. You can then ping the user who requested clarification to let them know of the edit.


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Why are there vortex generators under the Boeing 737's cockpit windows?
What is the purpose of the vortex generators located right in front of the Boeing 737's windshield?

Apparently, they are there to reduce the cockpit noise. From b737.org.uk:

Notice the 10 small vortex generators above the radome. These reduce the cockpit noise from the windshield by 3dB.

According to this document, the VGs, along with other improvements like damping/insulation changes, window frame improvement and ECS improvements contribute to a total noise reduction of 3 dB (at 35k ft and Mach 0.78). Though their exact impact is unknown, the reason for VGs are there is to reduce cockpit noise.

Ok thank you. But which way do they reduce noise?

@ECJCZ Basically, the angle between the fuselage and windshield creates a separation bubble, which causes unsteady pressure fluctuations on the window, leading to noise. The addition of the VGs reduces the size of this separation bubble and turbulent boundary layer, thereby reducing noise.

@ECJCZ See this paper. It's from guys in Boeing and I wouldn't be surprised if this modification was related to the paper.

aeroalias, so, in short,  the angle between the fuselage and windshield creates a separation bubble, that is to say, separation of the boundary layer occurs, producing uncontrolled turbulence which in turn produces noise in the cockpit. So, vortex generators are placed right there to avoid, or at least to delay the airflow separation and therefore noise. Is it correct?


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What is the definition of visibility as seen in aviation weather reports?
If you look at the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service (NWS) page for Washington D.C., Reagan National Airport (KDCA), it shows hourly weather observations proceeding back from present through time.
I notice that there has been 10.00 miles visibility all the way back to 17 August, where for one hour there was only 7 miles visibility. During these hours of 10 mi visibility, there are multiple conditions of cloud cover, ranging from Light Clouds, to Overcast, to Light Rain.
What is "visibility" when added to a weather report broadcast from an airport? It seems that if I am in the middle of Light Rains, well then my visibility cannot be "10 miles".

All my quotes for this post comes from FAA Order 7900.5C, the Surface Weather Observing Guide.
Visibility is defined as "Visibility is a measure of the horizontal opacity of the atmosphere at the point of observation and is expressed in terms of the horizontal distance at which a person should be able to see and identify specific objects."
All METARs report Prevailing Visibility, which is: "Prevailing visibility is the greatest visibility equaled or exceeded throughout at least half the horizon circle, which does not necessarily have to be continuous. This is the visibility that is considered representative of visibility conditions at the station."
Automated stations, generally report a max visibility of 10 SM. Now if you look at stations that are completely manual, i.e. KBJC(when I worked there it was a completely manual station), we'd report anywhere up to 70SM or higher visibility, due to our visibility markers.
-RA can often be easily seen through, RA or RA+ do become harder to see through, and as always, it can be dependant on where the -RA is, if it's only in a tiny quadrant of the horizon circle, it can often be a greater visibility.
[Edit Post comment about RA]: Sorry, used a few more abbreviations. SM = Statute Miles, which is like a regular mile that most people use in their daily lives. It's depicted as SM, due to most other things in aviation being in Nautical Miles.
-RA, RA, +RA, are the various descriptors for Rain. -RA means light rain, which if just using vis concerns is defined as, "From scattered drops that, regardless of duration, do not completely wet an exposed surface up to a condition where individual drops are easily seen." RA, is Moderate Rain, defined as: "Individual drops are not clearly identifiable; spray is observable just above pavements and other hard surfaces" and +RA is heavy Rain, "Rain seemingly falls in sheets; individual drops are not identifiable; heavy spray to height of several inches is observed over hard surfaces."
Also, METAR is the type of aviation weather report. METAR's are the hourly/standard report, and then there's SPECI's which if certain changes occur in conditions, from Freezing Rain, to changes in visibility or cloud ceilings, to massive wind shifts, to thunderstorms, to other factors, can be produced outside of the hourly/regular report.

Added more detail.

In most of the world outside USA, visibility is in metres with 9999 meaning at least 10 km (so there is no way to report more even if the station knew).

Yeah I came here because I was looking at weather and the visibility was "10000" which kinda threw me off because I thought it would be 10. So if I get ten thousans, that means 10K meters?

There is a good explanation from the National Weather Service about visibility.
The weather observation system measures the clarity of the air. This is done by measuring the amount of light scattered from a light source, such as a Xenon flash lamp, across a distance of 0.75 feet. This is measured every 30 seconds, and each minute is averaged over the past 10 minutes to produce the reported value. Although this is adjusted to allow for changing conditions, there will be some lag before the average reflects new conditions.
This system can differ from human vision for various reasons, and reflected light from precipitation is one possibility. Bright conditions will also cause the system to over-report visibility.
The perspective of surface observers will also be different from the view pilots have higher up.


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Botching crosswind landings
I'm having a terrible time nailing my crosswind landings. I'm a student pilot and have about 30 hours in a Cherokee 180 and working on my solo CC's.
I start out doing a side slip method on short final with my upwind wing dipped and using opposite rudder. All is usually great, up until I start my round-out. As soon as I start rounding out, I feel as if I'm using too much rudder to stay on center and fear I'm going to side load on touchdown. If I release some rudder pressure, I immediately start turning upwind and struggle to get back on centerline. If I compensate by releasing a little aileron input to compensate, I drift downwind.
Is there a technique I can use to get this figured out? Just more practice? My CFI keeps telling me the same thing "ailerons into the wind, opposite rudder" and can't seem to help me pinpoint what I'm doing wrong. Maybe time to try a new CFI?

If it puts your mind at ease in any way, at 300(ish) hours I still feel like every significant crosswind landing is pretty terrible. They're all safe enough though and I've managed to walk away from every one. Its just an unnatural thing to try to do, and requires you to go against your natural judgement of the controls.

I would find out if it were possible to have "too much rudder" with a Ckerokee 180.  The rudder controls where the nose points. That's it.  Ailerons hold you against the wind.  The real problem is the wind can change so please don't worry about being perfect, just keep flying the plane all the way down as best you can.  Typically you can land on one wheel.  You will only "side load" if you are drifting.

Keep in mind the wind can change even between 2 feet above the ground and 10, and if it does change, it usually changes to be calmer at the ground. You may in fact be holding too much aileron and rudder if keeping the same control inputs all the way down final to touchdown.

I feel as if I'm using too much rudder to stay on center

This part of your question suggests that you may have some misconception about how to judge what control inputs are needed during a crosswind landing.
From a pilot's practical perspective, during a crosswind landing using the "wing down" (sideslip) method, rudder controls heading, and ailerons control (via bank angle) the aircraft's sideways "drift" (either upwind or downwind), or lack thereof.
(From a fundamental point of view, that's not really what the controls are doing1, but when we include the pilot in the loop, in this particular situation, that's the net outcome.)
So you make rudder inputs as needed to hold heading, and you make aileron inputs as needed to stay on the centerline.
There's no "set" amount of aileron deflection that should go with any given rudder input, or vice versa.  (Well actually there is, at least for one given airplane, at one particular airspeed, flying in a perfect world featuring a crosswind that is totally smooth with no gusts etc-- but we don't live in a perfect world.) So just use the rudder, and ailerons, as described above, as needed.
Changes in one of the two control inputs (rudder or ailerons) will normally drive a need to vary the other control input as well, for reasons that are beyond the scope of this brief answer.  Don't worry about it, just continue to apply inputs as needed as described above.
You'll almost always find that you need to dial down the rudder and aileron inputs as you descend down through the wind gradient near the ground.  No problem-- just continue applying the corrections as needed as described above.
Another answer to this question has made an excellent suggestion for a practice exercise.
Footnotes:

This answer is aimed at aircraft of a basically conventional configuration, and more specifically, aircraft that generate some amount of net sideforce in the "downwind" direction when being flown in a sideslip.  But for a real "outside-of-the-box" mind-bender, consider the following: imagine a nearly all-wing aircraft with no fuselage, and a swept wing.  There is virtually no cross-sectional surface area that would generate a "downwind" sideforce in a sideslip.  Directional stability ("weathervane" stability) is entirely due to sweep.  There is an all-moving rudder/ vertical tail with no fixed portion, mounted on a slender tail boom, only a short distance behind the CG.  Due to the short moment-arm, the rudder must generate a lot of sideforce to generate a yaw torque to create a sideslip (i.e. to yaw the aircraft's nose out of alignment with the actual direction of the flight path and relative wind), and the sideforce from the rudder acts in the upwind direction in relation to the relative wind.  So the net sideforce during sideslipping flight is in the upwind direction, not the downwind direction as would normally be the case.  Imagine that this aircraft is on final approach in crabbed (coordinated, non-slipping) attitude, and the pilot then applies rudder to align the nose with the runway heading.  To cancel out the sideforce resulting from the deflected rudder, and balance the forces on the aircraft and keep the aircraft moving in a straight line, must the pilot bank the aircraft in the upwind direction as is normally the case, or in the downwind direction?  If the pilot attempts a last-minute "kick out the crab" style of crosswind landing without banking at all, and if the touchdown is accidentally delayed and the pilot continues to work the rudder as needed to keep the aircraft heading parallel to the runway heading, while keeping the wings level, will the aircraft "drift"-- i.e. will the flight path curve-- toward the downwind edge of the runway as would normally be the case, or toward the upwind edge of the runway?  The take-home lesson: with unusual aircraft geometries, "your mileage may vary", but the content of this answer is valid for all aircraft with even a remotely conventional configuration.

There's an exercise you can try (with a CFI) which helped me tremendously with developing the coordination and muscle memory to master crosswind landings. The exercise involves making a low approach, and applying your slip technique to "drift" back and forth from one side of the runway to the other.
There's a nice YouTube video demonstrating the maneuver. The demonstration starts near the 6 minute mark. I'd suggest watching this together with your CFI and, if they agree, giving it a try.
Pick a long, wide runway. Fly a normal pattern and final, but level off at a reasonable height, and add enough power to maintain airspeed. You don't want to be close to stall, but you don't want to be too fast either. Discuss this in advance with your CFI and agree on a target height and speed for the exercise.
During the exercise, your objective is to keep the nose aligned with the runway heading at all times. You'll constantly be adjusting the rudder to maintain this alignment, while varying your bank angle to control your lateral (side-to-side) drift.
After doing this a few times you should be able to develop a much more intuitive feel for how much "stick vs. rudder" is required to induce lateral drift. Then it's a natural step from inducing drift to counteracting it during a real crosswind landing.
Don't be discouraged: this is a very common pain point that a lot of students have to work really hard at. You just need to keep training your brain until it becomes natural. Stick with it, and you'll nail it.
Good luck!

I appreciate the advice! I'll show this video to my CFI and see what he thinks! It looks like a smart maneuver!

Besides the other answers, good ones as they are, I'm left with the obligation to remind you of the probably most important thing in landings - looking outside correctly: you need to focus your sight at the far end of the runway (or if the runway is looooong, maybe the middle of it)
Focussing on close proximity of the plane, like the aimed touchdown point, will make it harder to judge and manage control movements. Things go from bad to worse if you focus on the nose of the plane...
This may seem counterintuitive, and even difficult at first, but once your get this right, things should get easier to handle.
If you already are doing this correctly, just go with what the other answers suggest. You got this, just practise.

^^^This.^^^ Learning when to shift your view from the touchdown point to the far end of the runway is the real key to better landings. Work into that mental checklist along with reducing power and starting the the flare. Don't worry about small motion as long as you're moving straight down the runway and controlling the sink rate.

For me personally this was probably the most difficult thing to learn, and ended up being the biggest "improver" of landing performance.

You are probably over-thinking it, it's pretty normal so don't worry about it. Flying with crossed controls feels weird, and when you get close to the ground the picture looks wrong. You need to get used to that picture, holding it until you touch. There's no special sauce, it's just practice.
Don't worry about side-loads, it's designed to take it and you aren't going to break anything. It's far more important not to drop it on the runway. If you are doing the sideslip method correctly you won't have much in the way of side-load anyway, and if you aren't perfect it will not cause damage. Keep looking at the far end of the runway, and the centerline as far out in front of you as you can see. That centerline is your guide, if it's not moving left or right then you have the rudder right and there's nothing you need to do.
If you are a little bit right or left of it that's okay at first, once you get your technique down you'll be better at getting on centerline. The important thing is that you aren't going any further left or right of the centerline, and this is where you modify the rudder, if the centerline (in the distance) starts to move to the left put in a little left rudder, if it starts to move right squeeze in a bit of right rudder. Make small-ish adjustments rather than coarse changes, and keep the wing at the same angle.
Keep in mind you can practice this technique without a crosswind, it's used for flapless landings in many airplanes, talk to your instructor about trying it.

Perhaps having a motorcycle and no car helped me, but I never had any problem with this when I was taking lessons.
As far as I remember it felt natural right from the beginning.
(When landing, do you tip to the side in your seat in order to be perpendicular to the runway?  If so, don't.  You and the plane should be as one, not you and the runway.)
You seem to be too aware of the individual controls involved in this.
Your hands and feet should automatically do what is necessary without your thinking about it.
(When you're running and turn a corner, do you consciously think about how much you need to bend your knees to keep one leg shorter than the other in order to lean to the side and turn exactly the right amount?)
Just concentrate on the goal: the plane's being lined up with the runway.
That you happen to be tipped to one side or the other is irrelevant.
That, when you touch-down, you'll be riding on one wheel is irrelevant.
All I can suggest is to practice flying in unusual attitudes and getting a feel for how to maintain them.
And certainly when landing, start and maintain a side slip long before you need to.
By the time you get near the runway you will already be somewhat comfortable with it.


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Why do VFR-flights need a clearance in class D airspace?
I ask myself why VFR-traffic has to get ATC-clearances in class D airspace, because as far as I know, ATC doesn’t provide separation for VFR-traffic in this airspace class...
So why for example is a VFR pilot given the clearance (or is that an instruction) to maintain 4000 ft in class D airspace, if he is responsible for the separation, and not the controller?

Welcome to aviation.SE! Which country or regulations are you asking about?

Hello, I meant for Luxembourg, which is under the jurisdiction of the EU (SERA) and other, national, regulations. The AIP for Luxembourg is published by the belgian ANSP.

Because class D is controlled airspace.
While you are correct that VFR-IFR separation is not provided in class D airspace, the major advantage compared to class E airspace is that, because VFR is subject to a clearance, ATC knows exactly where all VFR aircraft are, enabling ATC to provide very accurate traffic information and/or collision avoidance.

So why for example is a VFR pilot given the clearance (or is that an instruction) to maintain 4000 ft in class D airspace, if he is resposible for the separation, and not the controller?

ATC can certainly limit you to a specific altitude, but as a VFR flight ATC can never lock you on a specific heading (since you must also be able to turn to stay clear of clouds). All rules regarding right-of-way in the air are based on turning - not climbing or descending - so being instructed to maintain a specific altitude should not limit your abilities to follow the normal rules of right-of-way.
Although not technically required, ATC will often provide some sort of separation between VFR and IFR in class D, at least in cases where there is an obvious risk of collision. But the normal separation minima do not apply, and ultimatively it is pilot responsibility to practise see-and-avoid (which is made significantly easier compared to class E or below because ATC can provide accurate traffic information).
If we go one step "up" the ladder, to class C - where VFR-IFR separation is provided - a major difference for VFR is the requirement for a mode A/C transponder. A transponder is normally not required in class D for VFR traffic, which is another reason ATC is not necessarily able to provide IFR-VFR separation in class D.
There are different use cases for the different airspace classes, and different countries and ANSP's will make use of them as they see fit in their local environment. The existance of the different airspace classes makes it possible to graduate the service provided to suit most situations:

Class G: No separation
Class F: No separation, but advisory service
Class E: IFR-IFR separation, no radio/transponder for VFR
Class D: IFR-IFR separation, radio+transponder required for VFR
Class C: IFR-IFR and IFR-VFR separation
Class B: IFR-IFR, IFR-VFR and VFR-VFR separation
Class A: IFR-IFR separation, VFR not allowed

Thanks, that already clarifies it... but where can I specifically find those regulations, apart from the different national AIP’s?

@FelixBraun ICAO Annex 11, or summarized here: https://www.skybrary.aero/index.php/Classification_of_Airspace - but be aware not all countries comply 100% with ICAO recommendations, so the national AIPs for the specific country is always the authoritative source. (AIP section ENR 1.4)

I‘ve taken a look at some AIP‘s, they all are more or less the same (in terms of airspace classification)... So if I‘m right, ATC instructions given to such VFR traffic are to separate it from other traffic, even if that isn‘t really the task of the controller?

@FelixBraun In practise, to a small extend, yes. But mainly to be able to provide accurate traffic information


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Rings around propellers
As a followup to Why do turbofan blade tips exceed the speed of sounds while prop tips should not my question is: why have rings on propellers not been used to overcome this problem?
It seems from this site that they are produced at least for maritime use.
According to this site and this site it seems to have advantages and experiments have already been done as I can see from the picture. (I do not know how reliable it could be though)

Propeller rings (ducted propeller) have been used un aircraft, notably in some early VTOL designs, like the Bell X-22, XV-11 Marvel and also the RFB Fantrainer.

Bell X-22. Image from diseno-art.com
They do have some advantages like,

Better noise reduction and safety compared to 'open' propeller.
For the same thrust, the propeller can be made smaller.
The duct can be designed such that it provides a limited amount of thrust vectoring, useful if we are using it for STOL.

However, they are not widely used because of various other reasons like,

For effecient operation, the tip clearance should be very small. Any increase in tip clearance leads to rapid degradation in effeciency.
The duct and its support structures increase the weight.
The duct increases the drag at cruise speeds (as drag increases as square of velocity).
If we decide to use a lower sized propeller as a result of using the duct, the effeciency suffers- as we are actually accelerating a lower mass of air more (rather than accelerating a higher mass of air less, which is more effecient).
The design of the duct is difficult- the aiflow into the duct comes not only from the front, but is also sucked from the sides from the sides (i.e. the capture area is greater than the duct frontal area). If not designed properly, the flow may seperate, leading to loss of effeciency.

However, ducted fans are used in a number of small UAVs (in RC model jet aircraft, for example, in lieu of miniature jets), electric aircraft like the Airbus E-fan and also some dirigibles.

In case you are asking about connecting the propeller tips like in the maritime propller in the link, the resulting stresses at high speed would tear the whole assembly apart, causing more problems than it solves.


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Are there differences in tool standards between aircraft manufacturers?
As a follow up to "What is the measurement system used in the aviation industry?" which specified about measurement units during operations, another question that comes to my mind is: are there differences used in tools for maintenance and repairs for aircraft produced in different countries?
Although things have been standardized these days, in the automotive industry you still get differences in the types of tools that are required for repairs. For example, the old British cars such as Land Rover or MG used imperial spanners until not long ago (3/8, 5/16 etc) whereas other cars used more common metric spanners.
Does this apply also to aircraft? An example that comes into my mind would be the Avro RJ series.

there are 2 main airliner builder, boeing and airbus, one is american the other is french

@ratchetfreak dont forget the Canadians (Bombardier) and Brazilians (Embraer)

@ratchetfreak The British, German and Spanish parts of Airbus might disagree with your characterization.

@casey this is really strange, Air canada doesn't seem to have any Bombardier in its fleet, but does have Embraer.

According to a friend of mine that has worked as an aircraft mechanic for the last 30 years or so, it depends on the manufacturer.  For example:

American made aircraft, including Boeing, use SAE sized tools (US standard sizes)
Airbus uses metric tools
Hawker uses British Standard Whitworth tools
Dassault Falcon uses (believe it or not) a combination of SAE and metric.
Bombardier uses SAE

got curious about embraer and bombardier...

@woliveirajr I added Bombardier but am not sure about Embraer, although I think that they are SAE too.

Hawker is still using Whitworth? Did they get a good deal on surplus fasteners when MG went out of business?


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How do airliners get from the factory to the client if the aircraft does not have the required range?
Today I flew on an Embraer 190 of Kenya Airways. Checking in the tech specs this aircraft has a range of roughly 2900 km. Considering it is built in Brasil, I was wondering how do they deliver it to Africa since they would have to cross the Atlantic Ocean which I suppose is more than 2900 kms of range it has available.
Do they add temporary tanks and, of course, by flying the aircraft empty get more range out of it?

My guess is that they fly up near Greenland so that they never have a leg that long, but I'm not 100% sure of that.

I answered your question without actually looking into the range of an E190, but according to the manufacturer's website, the range of the E190 is 4,400km, which will get you well into Africa from Natal, Brazil without tanks. http://www.gcmap.com/mapui?R=2400nmi%40sbnt&MS=wls&DU=mi

For the Greenland route the shortest leg of CYQX-BGBW-BIKF-EGPF is 1478 km. The runway at Narsarsuaq is not quite long enough for an E190 at maximum take-off weight, but the leg to Iceland is not the long one and you'd fly it with no payload anyway.

It's called ferry flying. This is related: What regulations surround fitting aftermarket fuel tanks inside the cabin?

I don't see anyone mentioning mid-air refueling - is this not practical with commercial aircraft?

@Yos233 maybe I read the tech specs on the magazine wrong but in any case the question still applies. Thanks.

@Superbest Mid-air refueling is expensive and I believe rather dangerous. It also requires an aircraft which is designed to allow it and experienced pilots. It's not really an option for commercial flight.

Dakar to Natal is only a bit more than 3000 km. With a stop in Cape Verde or some temporary measure to extend the range, the plane could fly it on its own. Planes can also be transported by cargo ship. I don't have any evidence that it's happening regularly (probably isn't, for economic reasons) but ships can transport many many things and even a fully assembled plane wouldn't be a big problem.

Possible duplicate of How are GA aircraft ferried from factories?

I was on Midway Island once when a flock of Cessna Skymasters (http://www.337skymaster.com/images/jerry337S.jpg) landed for refueling on the way to Vietnam. Besides the regular tanks, each plane carried fuel bladders in the passenger compartment.

Sometimes they do add temporary tanks. Here's a picture of what Hawaiian Airlines had to do to get their fleet of 717's over the Pacific because they did not have the range.
I don't have the answer to your question specifically, but I would guess they either add temporary tanks and go from SBNT-GUCY which is not much further than max-range, or take the long haul through the US and Europe.
There's a Cranky Flier blog post about this.

Out of interest how much fuel is there in those internal fuel tanks compared to what it would normally carry. I have no idea how much fuel a standard aircraft would take so wondering if that is 10% more or 100% more fuel...

I'm estimating each tank is 8ft by 4ft, which gives a total volume of 11,400L. Jet Fuel is measured by mass (0.81kg/L), which is 9220kg. That is approximately an additional 80% fuel capacity.

According to Wolfram|Alpha, that is about 1.5 elephants mass. Pretty heavy.

How did they fit those tanks through the aircraft's doors?!

What did they do with all the seats they had to remove??

@FreeMan The interior presumably isn't fitted until the plane reaches its destination. It can be delivered separately (e.g., in a larger plane or just in a shipping container) and even acquired separately.

First of all, yes, there are tricks to get the aircraft fly farther. You can leave the payload out, this will allow you to fill all fuel tanks without reaching the maximum take-off mass. Less mass means less induced drag, so you can fly higher and at a lower fuel flow. It will also allow you to install temporary tanks to carry even more fuel than the aircraft was designed for. That is how small GA aircraft get transferred from the US to Europe.

This is a typical payload-range diagram with the three distinct points: Maximum payload, maximum fuel and transfer range with no payload. The slope between maximum payload and maximum fuel points shows how well the additional mass of fuel is converted into range (mostly due to engine efficiency), and the slope of the lower segment between maximum fuel and no payload shows how much the weight reduction increases range (due to induced drag reduction).
In jets and turboprops, you can use higher-density fuel (PDF) which gives you more energy per volume in order to get a few more percent of range. And if all fails, you can disassemble the aircraft and ship or fly the parts over. If the range is not sufficient, the plane will be small enough and will be designed for easy dis- and reassembly.

Short Belfast being loaded with JetRanger (own work)

extending the leg between max payload- max fuel (replacing the payload with fuel) that graph would get to ~13000 km

@ratchet freak: Good remark! By adding tanks you can stretch the range to this point without exceeding the maximum take-off mass (almost - the tanks add some mass themselves).

I flew in a brand spanking new Airbus A320 on its maiden voyage from Toulouse, France to New York about 13 years ago.  We had to stop in Iceland and Newfoundland for fuel before heading to New York.
At Oshkosh every year (EAA Airventure) I hear about pilots crossing from Africa (the furthest western point) to the furthest eastern point of Brazil in a single engine small plane.  So I'm betting the jet can easily make that crossing.  They do have to put down at the first airport to get fuel.  That flight is not one I'd care to do...

The closest route I could find Africa-South America is GVNP..SBFN, which is 1242NM and that sounds like it's well out of range for any small GA piston single even with the cabin full of fuel. But I might be mistaken. Both are island airports with the shortest runway being 5900ft. Either way it's a pretty bad idea, even if you have the range when the winds are calm... :)

5900 is great for a decent sized jet.  The runway at my home GA airport is 3800 feet and we have G5's coming in regularly.  There's a few articles out there on small planes crossing the atlantic via Africa (I didn't say it was smart in a single engine :)  Check out this 150 (very small piston) crossing the atlantic with an extra tank link  The endurance record was set last year when a Lancair flew from Guam to Jacksonville Florida (7000 nm) Here's a link to the story: [link]http://www.eaa.org/news/2013/2013-03-05_long-distance-lancair.asp

An Australian company I used to work for purchased a Jetstream 41 turboprop off an American seller. With a range of only about 1400 kilometres, there was no chance of safely making it across the Pacific. So the ferry flight went through Canada, Alaska, Russia, right down through south Asia to northen Australia.
So the answer is, when they can't extend the range far enough, they'll go the long way!!

Nice gig if you can get it. :-)

I was chatting to one of the Pilots of Maldivian Air Taxi a number of years ago, who fly Canadian built Twin Otter's. He remarked that one of the more interesting jobs for that carrier was the "Overhaul flights". A few pilots spend almost all year ferrying their aircraft back and forth to Canada.
I don't remember the exact route but it involved lots and lots of stop-offs for fuel.


text:
Does an IFR flight-plan include the approach?
I tried to create an IFR flight plan (at simbrief.com) and there is something I don't get:
Are we supposed to know the runway/approach at the destination airport before taking-off, and add it to the plan?
Suppose I want to land at LFPG, the end of the route looks like this:

As you can see, the route is not matching any runway... The pilot is expected to divert from the planned route for the approach, if so, when? It seems that you can't use ILS in these conditions, so what happens with the FMC if you feed it with this flight plan? You should disconnect and divert manually for the approach, and when?
The route simbrief gave me looks like this: LSGG SIRO7N SIROD UH10 DJL DJL8W LFPG

Are you asking for flightsim or real flying?

I'm asking for flightsim, but I don't expect it to be much different from real flying.

Consider joining a flightsim community such as www.vatsim.net. They will be able to help you out on flightsim questions.

@StephenS There is no difference in this regard in the flight plan between these two. (Ignorring all the obvious differences of a game and real flying.)

@VladimirF There is a difference in the OP’s knowledge we can assume when answering.

You will leave the airway early before LFPG, and use an arrival procedure to reach the runway. Actual arrival will depend on the wind direction and for a TMA with multiple airports, which is the case of Paris, on the other airports direction of operations, at the time of landing (not at the time of planning). Look at the different arrivals (noted STAR for standard arrival) here.

US-based answer. No, the specific instrument approach is not part of the flight plan and is not included in the initial IFR clearance.
The flight plan is just that, a plan. It can change in flight, due to weather, immediate traffic, traffic congestion (enroute or at the destination), or pilot's request. If an airport has a Standard Terminal Arrival Route (STAR) it is common to receive a clearance including that STAR, but because many if not most STARs are specific to an arrival direction and/or a landing direction it is not uncommon for the filed/issued STAR to be changed before the flight arrives.
It used to be the case (and I believe is still suggested in the AIM) that a pilot should file a flight plan that terminates at an Initial Approach Fix for a specific approach to the destination airport. This is important for lost-comm procedures; the pilot would hold over the IAF until reaching their estimated arrival time, and then proceed to fly an approach. This technique was probably easier when a single navaid at the field could be the IAF for multiple approaches; today, with ILS and especially RNAV approaches being far more common than VOR or NDB approaches, filing this way is exceedingly uncommon. Instead, a pilot files and is cleared either via a STAR (which might terminate at the IAF for a specific approach, or with radar vectors to an approach) or direct to the destination airport (in which case they must receive vectors to an approach).
In terms of actually flying the plane, yes, the pilots would "deviate" from the filed flight plan when ATC issues other instructions, such as a clearance direct to an RNAV IAF, or vectors to the final approach course of an ILS. When that happens the pilot may elect to fly the plane manually, or may modify the route in the FMS to fly directly to the specified IAF, or may set the autopilot to heading mode so as to fly the specified vector.
There is no reason to assume an ILS approach (or any other type of approach) is impossible, simply because it is not on the originally filed flight plan route.

What you’re missing is that DJL8W is a Standard Terminal Arrival Procedure (STAR) to the Paris area.  Here is an (out of date) chart:

This procedure takes you from DJL to OKIPA, which is an Initial Approach Fix (IAF) for all of the Instrument Approach Procedures (IAP) into LFPG.  For instance, here is an (out of date) chart for the RNAV 27R:

In the real world, you won’t know which approach to select at the time you build your flight plan since that will vary with traffic and weather, so you just file up to the STAR and then wait for ATC to tell you what approach you’ll be using when you get there.

Looks like the exact information the OP was missing.

authors: Vladimir F Героям слава


text:
Cargo fire risk
If there is a fire due to a lithium battery in the cargo hold, can modern day technology in passenger planes; fire proof panels, Warning system, oxygen starvation, compartmentalisation, fire suppressants (although I've read halon gas is not effective at extinguishing a lithium battery fire) contain (or even better extinguish the fire) long enough for the pilot to do an emergency landing from 40,000 ft?

"Halo" gas? What's that?

@RalphJ Probably Halon 2402, a fire suppressant, or one of its more environmentally-friendly replacements.

The answer is a complicated "Not always, but yes, but probably".
Let's uncomplicate it. First, bad news: Lithium battery fires are difficult to extinguish: they don't require oxygen to burn, and small amounts of water can react with the chemicals to release hydrogen. Fire suppression on passenger airliners uses a fire reaction inhibiting agent (Halon or Novec), which won't extinguish the lithium fire itself, but can stop or slow down the spread of that fire across less-flammable cargoes.
Good news: Lithium fire extinguishers do exist. Some are based on vermiculite-water dispersion. But these extinguishers aren't very capable.

Note how this 400 ml/ 1 kg unit has to be directed at the device, and yet is only approved up to 60 Wh, about two cell phones, while modern laptops range from 75 to 99 Wh. There's no possibility to protect the entire cargo hold this way - the extinguishers would weigh as much as the cargo.
Large commercial lithium battery transport and storage operations use water mist based fire suppression. It works, and it works even in a warehouse, without being directed at the source. But it requires some amount of water and some high-pressure pumps.

Bad news: These water mist systems aren't fitted to aircraft. It would be possible to some extent, since there is already a water tank onboard, and pumps are similar to those used for hydraulics, but it would add weight, and likely be difficult for a retrofit. Maybe someday, when you simply can't legally buy shoes without 8G connectivity, RGB lighting, NSA step-tracking and a lithium battery built in anymore, new planes will be designed with lithium-capable fire suppression as standard. So far they're not.
Good news: Almost all lithium battery fires happen inside the passenger cabin, where they can be taken care of. There have been no cases of lithium fires starting inside a passenger airliner's cargo hold so far. Should it happen, the airliner's fire suppression should be able to reduce the rate of spread of fire long enough to land, or stop it altogether. But there's only enough fire suppression agent for one of the (two) cargo compartments, it's sized for the average expected conflagration.
One reason there haven't been such fires is the rules about only taking batteries and battery-containing devices in carry-on. Batteries alone, outside a device, are barred from transport in passenger aircraft holds. There are lithium-safe containers, and, if your airliner is transporting goods containing lithium batteries commercially, they should at least be in a fire-resistant container.
So-so news: Fires are unpredictable. The fire can self-extinguish, or it can start in a suitcase or a container filled with highly flammable items, and damage something vital before the fire is suppressed; the systems can be misoperated or malfunction. The standard operating procedure in case of a cargo hold fire is to LAND IMMEDIATELY, but planes often fly over the ocean, where it just isn't possible.
Conclusion: There's no guarantee the airplane will have enough time to land. Generally, they are designed to be able to do so, but once a fire does start, the remaining safety margins are fairly thin.

It would be useful to include information on how many lithium fires have occurred in cargo holds and how many times they have resulted in injury.

@DJClayworth None that I know of. However, that's why we can't tell for sure what happens when they do. With weekly cabin fires, we know the worst-case is forced landing due to smoke, the best case is the phone gets tossed into a container. No such dataset for hold fires.

Bad News Your future-spec shoes won't make it through security screening, so they won't be a fire hazard in the future, either... ;)

Li-ion fires are annoying in that involve chemical reactions that may continue even after using fire suppression.  Sometimes batteries will self-ignite hours later.  This is a tough problem to solve: We want our batters to be good at storing/releasing energy...except when we don't.  The FAA has good reasons to be paranoid about this stuff.

@FreeMan Unless NSA overrules FAA, because smart shoes are so awesome for people tracking ;)

Good point, @Therac. Actually, that'd be a challenge... Am I at home where my spare pair of smart shoes are, or am I out where my smart phone is? Hmmmm..... :D

I found an example of lithium fires in cargo hold that caused fatalities: UPS flight 6.


text:
What frameworks exist to assess piloting skills and ability and how can one assess themselves against these?
What are the existing frameworks and methodologies used to evaluate and measure piloting proficiency, and how can individuals effectively assess their own skills and knowledge based on these established standards? Furthermore, are there established methodologies for self-assessment that align with these frameworks, enabling pilots to enhance their skills and competence?

Hello! It looks like this question would be better suited for a forum rather than a Q&A site. https://pilotsofamerica.com is a popular one; although most users are American, users from any country are welcome there.

Without the meta commentary, this question is only its last paragraph. That paragraph contains two sentences, both of which are too broad for Stack Exchange. Neither is particular to Aviation, either, "how do you keep getting better at X?" is broadly about habits and mindsets that aren't related to X itself.

In 4 words: fly with other pilots.

Voting to reopen.  This is not opinion based, and answerable thanks to the excellent edit by Tedious Tortoise.  https://www.faa.gov/training_testing/testing/acs

On MS Flight simulator, you get a Grade for landings on landing challenges :D

To effectively evaluate and measure piloting proficiency, there are established frameworks and methodologies used in the aviation industry. International Civil Aviation Organization (ICAO) has developed core Human Factors documentation that outlines the essential competencies for pilots. Many airlines use these competencies as a basis for evaluating their pilots' performance during training, assessments and line checks.
The core competencies established by ICAO are as follows:

Application of Procedures: Applying the correct procedures during all stages of flight, both in normal and non-normal situations.

Knowledge: A thorough understanding of aircraft systems, performance, and procedures.

Flight Path Management - Manual Handling

Flight Path Management - Automatics: Pilots must also be proficient in handling automated systems and flight management.

Communication

Teamwork and Leadership

Problem Solving

Workload Management: The distribution and prioritorisation of tasks, procedures and checks.

Situational Awareness: A clear understanding of the aircraft's position, surroundings, potential threats.

Perhaps with the exception of Flight Path Management - Automatics, the competencies mentioned above are universally relevant for all pilots, encompassing both VFR and IFR flying scenarios, as well as single or multi-pilot operations.
Its is very good practice to consider each of the competencies above as perform a self-assessment. By thoroughly evaluating each area, individuals can identify areas for improvement and recognise their strengths.
I recently had a conversation with the head of training at my airline's training center, and his perspective resonated with me. He emphasized that the best pilots are those who can confidently and objectively answer the question, "What are your strengths and weaknesses?" He suggested that they do so by closely examining themselves against the core competencies (listed above), providing detailed and accurate assessments of their performance and areas for growth. This level of self-awareness and alignment with established standards are key elements in becoming an accomplished pilot.
Underlying the core competencies, it is essential that pilots maintain good “Knowledge, Skills and Attitudes” (cf. ICAO’s definition for ‘airmanship’ across much of it’s documentation). These are the driving forces behind improvement, see Skybrary’s - Competency Based Training article
Regarding Crew Resource Management (CRM), it is essential not to underestimate its significance. While some CRM training experiences may be uncessarily longwinded, a correct understanding and implementation of CRM are crucial, particularly in multi-pilot operations. CRM promotes effective communication, teamwork, and decision-making, contributing to overall flight safety.
In summary, pilots can effectively assess their skills and knowledge by aligning themselves with the competencies outlined by ICAO, having a good attitude to seek continuous improvement, and engaging in effective self-assessment. Embracing the principles of CRM is also vital to enhance piloting skills and competence, especially in multi-crew environments.

References:

ICAO Safety Management Manual (Doc 9859)
ICAO Manual on the Regulation of Flight Crew Licensing (Doc 9683)
ICAO Annex 1 - Personnel Licensing


text:
Airline pilots and unplanned but not necessary manouevres
This story details how an EasyJet captain flew a presumably unplanned circle to give everyone on board a look at the Northern Lights.
Are captains allowed to do this sort of thing on a whim, or would he or she have cleared it with ATC somewhere first ?

The easyJet would be operating under Instrument Flight Rules (IFR) and most probably in controlled airspace.

3.6.2.1 Except as provided for in 3.6.2.2 and 3.6.2.4, an aircraft shall adhere to the current flight plan or the applicable
portion of a current flight plan submitted for a controlled flight unless a request for a change has been made and clearance
obtained from the appropriate air traffic control unit, or unless an emergency situation arises which necessitates immediate
action by the aircraft, in which event as soon as circumstances permit, after such emergency authority is exercised, the
appropriate air traffic services unit shall be notified of the action taken and that this action has been taken under emergency
authority.
ICAO Annex 2 — Rules of the Air

The crew would be required to seek clearance from the air traffic control unit before deviating from the established flight plan or previous clearance. (i.e. they would have been on a set course and set altitude).
Deviating without proper authorisation would not be standard procedure and could lead to potential safety risks or conflicts with other air traffic.
Furthermore, I’m not sure if this would have gone down very well with the easyJet operations team - increased fuel burn and potential to run late. However, the article does suggest that easyJet supported the move, though this could have just been a comment from the PR team.
(Also, I just wanted to highlight that decision-making in multi-pilot aviation involves both pilots, not solely the captain. While the captain serves as the final authority in making critical decisions, it is essential to recognise that the flight crew operates as a cohesive team. You make it sound like one person is calling all the shots here).

Thanks - I reckon Ryanair would deduct the fuel from their salary :)

No don’t be silly…….they would charge the passengers €50 per head for the “Northern Lights Experience.”

As for the fuel consumption and delay: flying a circle to offer passengers a perhaps unique experience is well worth the whopping couple of minutes of time it takes and $150 it costs.

@Jpe61 I’m not sure a job in ops for a low cost airline is for you my friend. At least, don’t bring this up in the interview.

@tedioustortoise: If the plane was ahead of schedule, and might have needed to circle later in the flight as a consequence, perhaps circling at higher latitudes might require less fuel per minute because of lower exterior temperatures than circling nearer the destination?

@supercat Typically the airports easyJet tends to land at will not have any issue with taking a flight in early. No requirement to hold later in the flight

@supercat a very good point!  If the winds are better than planned, they may arrive at the destination airport before their landing slot or gate would be ready.  So they'd be doing tracks anyway, just showing scenic Dumpsville instead of the Northern Lights. And what altitude are the hold stacks?  Not 35,000 feet I'll bet, so they'd be less fuel-efficient.

@Harper-ReinstateMonica: I was being a little facetious with my suggestion, but making an extra circle at one part of the trip doesn't always imply using more fuel.  A bigger issue is that from what I understand the perceived need for air traffic control was a result of planes making slight sight detours over the Grand Canyon to give passengers a better view.

@Harper-ReinstateMonica just FYO landing slots or “gate ready” is really not applicable for the destination airports that easyJet would be landing into. If they are early, I can guarantee you the airports will almost always accept them without any issues.

@tedioustortoise That could well be. Mentally I equate them to Spirit or Southwest, which prefers quiet airports but flies into very difficult ones as well.

@tedioustortoise thanks for the advice

@Harper-ReinstateMonica a quiet airport doesn’t guarantee lack of difficulty, often it’s the opposite: short landing distances available, VFR traffic, less experienced controllers. (Context here is Europe)

If they were coming from Iceland, they weren't in the North Atlantic Track System.
If they were on the NATs (North America to Europe non-stops only), this would have been out of the question, but on a non-NAT route well to the north like that, the option would have been available, but they would still get a clearance from the applicable Oceanic Controller before doing so.

They were smack in the middle of the ADS-B/SSR surveillance corridor between Iceland in and the UK. The turn was executed at FL370, in the nominal coverage of two SSRs (one Icelandic, one on the Faroe islands) three terrestrial ADS-B stations (one Icelandic, two on the Faroe islands) plus the space based Aireon ADS-B system, all feeding data to Iceavia control centre in Reykjavik. This is not Non-Radar airspace

Though I suspect they got a call from the chief pilot the next day, asking why they were wasting gas out there!

@DeltaLima  I forgot all about ADSB lol. It's been 13 years since my last IFR flight.

ATC's job is to keep airplanes from crashing into each other. They have no interest where a plane goes or what route it takes unless it interferes with other aircraft or with safety. Obviously it depends on the situation like in a TCA, and some amount of order is necessary. I'm interested in the concept of "getting permission" from ATC. Of course, in controlled airspace ATC ultimately decides, but I would think a controller can't deny a pilot's request "just because I don't want you to".  They may not like the additional workload, but if no other aircraft are affected why is it their concern?

@StevePemberton well they didn’t have a problem with it hence why the manoeuvre was allowed. Remember though that this is IFR flight, with a legal framework for the conduct of the flight, the traffic simply is controlled. For example, I can’t just drive my car any which way I want to on the road, I have to follow the rules of the road. Even though I might think it is better to go through a red traffic lightit’s probably best not to. Typically air traffic control have the best situational awareness to handle the positioning of aircraft in the sky from a safety and efficiency perspective.

'@tedioustortoise - yes as I mentioned some order is required. And I am talking about Class A airspace not TCA's or similar. Standard routes have been implemented to create some orderliness. But variances to the standard routes happens all the time. Most  variance requests are limited to enroute weather and wind, but that's airline policy. My question is does ATC care about the reason for the request? A pilot can request a change from standard route due to winds, but not for sightseeing? They can request to fly in a circle to burn off altitude, but not to give passengers a view of something?

A pilot can ask for anything within reason, & ATC can grant it, or not , & will normally try to accommodate you if there aren't any traffic flow conflicts. An OEM will negotiate geographic test area blocks with local ATC unit & you'll be cleared into it & within you can go wherever you want. You can request all sorts of things, like altitude block clearances, & ATC will grant it or won't, depending on whether they can work traffic around you. Whatever it is, it's a clearance and you have to follow the clearance, and if you want to deviate outside its boundaries, you have to get permission.

@John K - Another example are things like the final maiden flight of the Queen. I would guess in some cases ATC will put you down into denser less efficient air where other airliners are less likely. Or in the 747 example it was under 18,000 feet and presumably VFR.  But what I am referring to is a common misconception that ATC decides what routes planes take. Yes ATC is always in control, but it's a subtle nuance in semantics which requires detailed explanation. Similar to the statement "airplanes can fly themselves".

When you submit your IFR flight plan, you choose the route. 99% of the time, ATC will issue a clearance based on your flight planned route. Occasionally, they will amend your flight plan and assign a different routing. You will be warned of this when you call in for your clearance, because instead of just jotting "FPR" as you write out your clearance to read back, you're going to have to write down and read back correctly a different set of waypoints. They will normally respect your IFR reserves range limitations, but if they don't, you have to let them know you can't use that routing.

@John K - I live about 5 miles from the corridor from the northeast into Atlanta, which includes planes from Europe if they aren't going north because of the jet stream. From watching FlightRadar24 it seems like ATC often starts getting everyone into the conga line for ATL just past Washington D.C. I'm guessing that the initial flight plan filed is essentially direct to ATL, or at least direct to the typical first waypoint for the approach. Then I would think ATC immediately amends it into the line they are using at that time. Or does the amendment usually occur en route?

Do some reading on STARs, Standard Terminal Arrival procedures. Large airports have published STARs, for different arrival directions, and navigation methods. When your clearance is issued, it may or may not include a STAR tacked on to the end of the route. It has a set of waypoints, altitudes and speed limits that get you from the last enroute waypoint to one of the instrument approaches for that airport. Arriving airplanes from a particular direction will always seem to pass the same spot b/c they are flying that STAR. IFR protocols are designed to allow you to complete a trip with no comms.


text:
Does propeller size affect total drag force of plane?
Integration of pressure distribution of  each blade  get net force(thrust) which is allways pointing forward.So there is no drag force at  any propeller ,that tells that size of propeller doesnt change total drag force.
So plane with propeller of 1m diameter will has same total drag force as plane with propeller of 2.5m diameter?
(if both planes are same and both propellers have same thrust force,and both propellers are fixed at tail so wash not blow at plane body,causing aditional skin friction and pressure drag)
boat analogy:
Why all speeds boats use small propellers,instead big ones?I allways think reason was big propellers increase boat overall hydrodynamic drag,but when I better think propeller cant cause drag when producing thrust!

This is a great question.  Propellers definitely have drag when they are not spinning.  There may be localized spots on the prop that are actually dragging rather than pulling under power depending on prop rpm and AOA.  Prop wash turbulence interacting with wing and fuselage airflow may also be considered.

@RobertDiGiovanni Why all speeds boats use small propellers,instead big ones?I allways think reason was big propellers have more drag,but when I better think propeller cant cause drag when producing thrust...

@RobertDiGiovanni, and propellers windmilling (spinning, but the engine not producing any power) create even more drag than propellers not spinning.

@member2017, boats use small propellers, because water being denser the induced power is low while the parasite power is high.

the drag force that a propeller generates while under power is expressed as a torque applied to the engine's crankshaft and arises because of skin friction on the propeller blade surfaces. as long as the prop is generating net thrust it is not generating drag in a direction opposite to its direction of travel.
Prudent design of the prop blades guarantees that no portion of the blade is ever generating backwards thrust for all possible combinations of airspeed, RPM, and blade pitch.
A propeller that is not generating thrust is generating drag which does act against the airplane's direction of travel.

I don't really like the sentence « there is no drag force at any propeller ». In fact, there is a drag force which could be overwhelmed leading to only net thrust (by projecting integrated force on flight direction).
Under your hypothesis: same net thrust, same plane and no interactions between aircraft and engine.. Yes you could consider the size of your propeller does not affect general drag.
Nevertheless, this is an interesting question and the distinction between drag and thrust could be headache, specially with integrated propulsion system. It is sometimes more convenient to think about power and energy getting in and out the system than forces applied to it. See Power Balance Method which was developed and presented by M. Drela.
Finally, note that even under your conditions (and as mentioned by @Robert DiGiovanni), there are other parameters than drag, limiting propeller (or more generally an engine) diameter:

Ground clearance: for practical and safety reason

Rotational speed: which reducing as prop diameter increase (for aerodynamic performance purpose i.e. shock waves at blade tip).1

Weight: which change the total lift needed by the aircraft

Noise constraints

Etc..

1
Moreover, for a gas turbine carrying the prop, reducing this speed involves turbine speed reduction (and so its efficiency) OR using a bigger gearbox (increasing the gear ratio) leading to an heavier and more complexe system (more energy to diffuse).